I've never replaced the springs on mine, but I have rebuilt the cylinders. If you are loosing tension on the tracks, I would think the cylinders need rebuilding. When I did this, the spring was loose and just resting there after all the tension had been taken off of the front idler. I don't think you will have to compress the new spring or the broken ones to get them off.
Can you show a close up picture of the actual broken spring?
Do you know if the cylinders are leaking or not? For sure?
Eddie
PS, It's not a dozer, but a track loader.